Cardiovascular disease, including atherosclerosis, is the leading cause of death in the United States. One method for treating atherosclerosis and other forms of arterial lumen narrowing is percutaneous transluminal angioplasty, commonly referred to as “angioplasty” or “PTA,” or “PTCA” when performed in the coronary arteries. The objective in angioplasty is to restore adequate blood flow through the affected artery, which may be accomplished by inflating a balloon of a balloon catheter within the narrowed lumen of the artery to dilate the vessel.
The anatomy of arteries varies widely from patient to patient. Often, patient's arteries are irregularly shaped, highly tortuous and very narrow. The tortuous configuration of the arteries may present difficulties to a clinician in advancement of the balloon catheter to a treatment site. In addition, in some instances, the extent to which the lumen is narrowed at the treatment site is so severe that the lumen is completely or nearly completely obstructed, which may be described as a total occlusion. Total or near-total occlusions in arteries can prevent all or nearly all of the blood flow through the affected arteries. If the occlusion has been established for a long period of time, the lesion may be referred to as a chronic total occlusion or CTO. Chronic total occlusions can occur in coronary as well as peripheral arteries. Chronic total occlusions are often characterized by extensive plaque formation and typically include a fibrous cap surrounding softer plaque material. This fibrous cap may present a surface that is difficult to penetrate with a conventional medical guidewire.
A number of devices have been developed and/or used for the percutaneous interventional treatment of CTOs, such as stiffer guidewires, low-profile balloons, laser light emitting wires, atherectomy devices, drills, drug eluting stents, and re-entry catheters. The factor that is most determinative of whether the interventionalist can successfully recanalize a CTO is the interventionalist's ability to advance a suitable guidewire from a position within the true lumen of the artery proximal to the CTO lesion, across the CTO lesion, i.e., either through the lesion or around it, and then back into the true lumen of the artery at a location distal to the CTO lesion.
The most common site of a peripheral arterial CTO is the superficial femoral artery (SFA). Lesions in this area tend to be long (20-30 cm) and involve bulky, calcified plaque which also includes atheroma and organized thrombus. Dr. Bolia developed a revasculaturization procedure as described in Recanalisation of femoro-popliteal occlusions: Improving success rate by subintimal recanalisation, Clinic Radiol, 40:325, 1989, by exploiting the subintimal space where a guidewire enters the subintimal space between the intima and adventitia layers, is subsequently advanced to a point distal to the occlusion, and then maneuvered to re-enter or puncture the vessel layers to enter the true lumen of the vessel. Once the guide wire has traversed through the subintimal layer and re-enters the true lumen of the vessel at a point distal to the occlusion, percutaneous balloon angioplasty is performed to restore blood flow through subintimal recanalization.
Different devices have been developed for facilitating re-entry into the true lumen when using the subintimal approach of bypassing a CTO, such as the PIONEER® catheter system by Medtronic, Inc. Some of these re-entry devices may be complex and quite expensive. Accordingly, in many cases, the procedure is performed by forming a loop in the guidewire as it is advanced in the subintimal space, and then bluntly dissecting the intima using the loop to re-enter the true lumen distal of the occlusion. The loop formed by the guidewire is generally stiffer than a distal tip of the guidewire. Further, the loop is generally formed naturally by the forces of advancing the guidewire through the subintimal space acting on the flexible tip of the guidewire. However, rotation of the guidewire does not ensure that the loop is directed in the proper direction, i.e., towards the true lumen. Further, the loop may slide distally such that it is not successful in rupturing the intima layer to re-enter the true lumen. In some instances, the loop may be lost as the guidewire regains a straight shape during the procedure.
Accordingly, there is a need for an improved device and method to create a subintimal lumen from the true lumen of a vessel on a first side of an occlusion to the true lumen of the vessel on a second side of the occlusion.